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Potassium chromate is the inorganic compound with the formula K 2 CrO 4. This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.
Sodium chromate is the inorganic compound with the formula Na 2 CrO 4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and deca hydrates . It is an intermediate in the extraction of chromium from its ores.
Potassium chromate is added as indicator in an Erlenmeyer flask and the end of the reaction is determined by the slight red color given by the silver chromate. In the Mohr method, named after Karl Friedrich Mohr , potassium chromate is an indicator, giving red silver chromate after all chloride ions have reacted:
Partial predominance diagram for chromate. Molecular chromic acid, H 2 CrO 4, in principle, resembles sulfuric acid, H 2 SO 4. It would ionize accordingly: H 2 CrO 4 ⇌ [HCrO 4] − + H + The pK a for the equilibrium is not well characterized. Reported values vary between about −0.8 to 1.6. [4]
Crocoite is a mineral consisting of lead chromate, Pb Cr O 4, and crystallizing in the monoclinic crystal system. It is identical in composition with the artificial product chrome yellow used as a paint pigment.
Sodium chromate (Na 2 CrO 4) Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO 5) is formed, which can be stabilized as an ether adduct CrO 5 ·OR 2. [6] Chromic acid has the hypothetical formula H 2 CrO 4. It is a vaguely described chemical ...
The hydrogen chromate ion may be protonated, with the formation of molecular chromic acid, H 2 CrO 4, but the pK a for the equilibrium H 2 CrO 4 ⇌ HCrO − 4 + H + is not well characterized. Reported values vary between about −0.8 and 1.6. [4] The dichromate ion is a somewhat weaker base than the chromate ion: [5]
Silver chromate is an inorganic compound with formula Ag 2 CrO 4 which appears as distinctively coloured brown-red crystals. The compound is insoluble and its precipitation is indicative of the reaction between soluble chromate and silver precursor salts (commonly potassium / sodium chromate with silver nitrate ).